Dyeing acrylonitrile fibers with acid dyes, a cupric salt and a naphthol compound



2,812,998 Ice Patented Nov. 12, 1957 DYEING ACRYLONITRILE FIBERS WITH ACID DYES, A CUPRIC SALT AND A NAPHTHOL COMPOUND Cyril G. Evans and William T. Rainey, Jr., Clemson,

S. C., assignors to Deering Milliken Research Corporation, Pendleton, S. C., a corporation of Delaware No Drawing. Application October 12, 1953, Serial No. 385,684

16 Claims. (Cl. 8-55) The present invention relates to dyeing of textile materials and more particularly to methods of dyeing textile materials containing synthetic acrylic fibers and to new and novel dye baths suitable for use therein.

In recent years it has been found that acrylonitrile can be polymerized r copolymerized with small quantities of other vinyl type compounds and the resulting products employed in the formation of acrylic textile fibers having advantages over textile fibers previously available. As a result of these advantages the acrylic fibers have enjoyed considerable commercial success and at present are marketed under a variety of trademarks including Orlon and Acn'lan.

One disadvantage of the acrylic fibers is that they are in most instances difiicult to dye and in fact cannot be dyed in permanent deep shades by the techniques employed for dyeing other textile materials. This has necessitated the development of special methods for dyeing them. While several such methods have been developed, the method of dyeing acrylic fibers believed to be the most widely employed today is known as the cuprous ion method. While this method of dyeing acrylic textile materials is generally more satisfactory than other prior art methods in that it allows oneto employ acid dyes to give fast colors and is capable of giving deep shades, it nevertheless suffers several disadvantages well known to those skilled in the art. The most serious disadvantage is that the method requires such close control that it is very difficult to obtain satisfactory and reproducible results.

This invention overcomes the difiiculties' experienced with the cuprous ion method, as well as the ditficulties experienced with other prior art methods of dyeing acrylic fibers, and provides a relatively rapid, simple method for dyeing acrylic fibers in any desired shade with acid dyes. The colors obtained by the new process are in most instances of a desirable brightness, fast to light and washing, and even very heavy shades can be obtained without dilficulty on pure acrylic filament. A further advantage of the new process is that it is not subject to the close control required of the cuprous ion method and eliminates the necessity of an organic reducing agent such as hydroxylamine sulfate.

According to the method of this invention, textile materials containing acrylic fibers are dyed by immersion in a dye bath comprising an aqueous mixture of an acid dyestuff, a naphthol compound and a soluble cupric salt.

It had been previously supposed that the presence of cuprous ions in the dye bath was necessary for the dyeing of acrylic fibers with acid dyestuffs, but in the dye bath of this invention no measures are taken to produce cuprous ions. It is apparent, however, that the new process involves more than the simple substitution of cupric ions for the cuprous ions of the prior art since the presence of the naphthol compound is an absolute necessity and little or no dyeing is obtained in the presence of cupric ions alone. The exact mechanism by which the naphthol compound acts is difficult to determine, but it is evident that it has the ability to cause the absorption of copper onto the acrylic fibers from a dye bath containing copper only in the cupric valence state.

The process is applicable to staple or continuous acrylic filament prepared from polyacrylonitrile or from copolymers of acrylonitrile with small quantities of other compounds. Textile fibers can readily be prepared from copolymers of acrylonitrile with not more than about 15% of a second polymerizable material as illustrated by vinyl acetate, vinyl chloride, esters, or other derivatives of acrylic or methacrylic acids, styrene, methyl vniyl ketone, and vinylidene chloride. Such fibers generally suffer an inability to be readily dyed with acid dyestuffs and the process of this invention is, therefore, of value for dyeing these as well as those formed from pure polyacrylonitrile.

The new process is also of value in dyeing blends of the acrylic fibers with wool or other textile materials although some difiiculty is frequently encountered in obtaining a union. Wool has a strong atfinity for acid dyes and when dyeing mixtures of wool and acrylic fibers, there is a tendency for the dye to be preferentially absorbed by the wool and it is generally necessary to slow the absorption of dye by the wool by, for example, a process such as disclosed in copending United States application Serial Number 385,683 filed concurrently herewith, now abandoned, if a true union dyeing is desired.

Substantially any dye of the well defined general class known as acid dyes can be employed in this invention. It has been found, however, that the mono-sulphonated acid dyes generally give the most satisfactory results. Suitable dyes for use in the new process can be illustrated by Anthraquinone Biue SKY (C. I. 1088), Anthraquinone Green GN (C. I. 1078), Orange II (C. I. 151), Quinoline Yellow PN (C. I. 802), Anthraquinone Blue RA, and Anthracene Blue WR (l, 2, 4, 5, 6, 8 hexahydroxyanthraquinone), as well as acid dyes sold under various trade names as Roracyl Orange R, Roracyl Dark Green B, Pontacyl Fast Red AS (C. I. 176), Pontacyl Rubine R (C. I. 179), and Roracyl Violet 2R. Of course a mixture of dyes can be employed if desired.

The concentration of dye in the bath when employing the process of this invention may be varied within wide limits as in conventional methods of dyeing. For instance, if one is interested in obtaining only light tints, the dye bath may contain as little as 0.25% dye based on the weight of material to be dyed; and if one is interested in obtaining dark shades very rapidly, the dye bath may contain as much as dyestuif based upon the weight of fabric. As a general rule, however, the dye bath should contain from about 1 to 10% dye based on the weight of fabric or raw stock.

Almost any water soluble cupric salt can be satisfactorily employed in the new process, although it has been found that the use of copper sulphate is the most economical and for this reason is usually preferred. Illustrative examples of other water soluble cupric salts which can be satisfactorily employed are cupric nitrate, cupric acetate and cupn'c chloride.

of copper salt employed in preparing the dye bath may be varied Within wide limits, and in fact satisfactory dyeings have been obtained Where a quantity of copper salt equal to 30 times the weight of dyestuff has been employed. In some instances, however, where a large excess of cupric salt is employed, there can be observed upon the resulting fabrics a slight copper tinge and for this reason and for economical reasons, the use of an excess of cupric salt is generally not advantageous. The optimum quantity of copper salt to be employed is that amount which Will just result in the exhaustion of the dye bath. This quantity has been found to be from about /2 to 2 times the weight of dye employed, if the 'dyestufli is mono-sulphonated, and approximately twice this amount if the dyestuff is a di-sulphonated dye.

Either alpha-naphthol or beta-naphthol can be em- .ployed in the new process of this invention; although it has been found that beta-naphthol gives slightly better results in some instances, and it is usually preferred for this reason. In addition to alpha and beta-naphthol, one can employ simple derivatives of these compounds wherein the naphthylene nucleus is substituted by lower alkyl, halogen since such substituents do not materially change the physical and chemical properties of the naphthols, and for this reason it is intended that the phrase -a naphthol compound as employed in the specification and claims be defined to include these simple derivatives as well as alpha and beta naphthol.

The concentration of the naphthol compound may likewise be varied within wide limits. Satisfactory results can be obtained in some instances employing as little as 0.5% naphthol compound based upon the total weight -of material to be dyed, and on the other hand satisfactory results have been obtained when the weight of naphthol .compound employed was as much as 100% of the weight of fabric to be dyed. If, however, one employs too little naphthol compound, good exhaustion of the dye bath may not be obtained, and the dyeing time may be unduly prolonged. On the other hand if one employs a large excess of naphthol compound, staining of the textile material may result and, this is especially true if a blend of wool and acrylic fibers is being dyed. In addition the use of a large excess of naphthol compound may result in the dyed material having a poor hand. For these reasons the optimum quantity of naphthol .compound to be employed is that amount which just results in the complete exhaustion of the dye bath. While this quantity will vary with the type and amount of impurities in the dye bath, the type of dye being employed .and the nature of the acrylic material being dyed, it is quite possible to employ a near optimum quantity in each instance regardless of the particular circumstance involved since the naphthol compound need not all be added at the start of the dyeing operation and one can add further quantities as the dyeing progresses if it is apparent that more is needed. As a general rule it will be found that a quantity of naphthol compound equal to from 2% to based on the total weight of material being dyed will give best results.

In addition to the acid dyestuff, the cupric salt and the naphthol compound, the dye bath may if desired contain other materials to accomplish a special purpose or to aid in dyeing. For example, it has been found that slightly brighter shades can sometimes be obtained if a small quantity of an organic solvent for the naphthol is added to the dye bath. Likewise, one can add other dye assistants, although it has been found as a general rule that the addition of other dye assistants is not advantageous and results in a loss of efiiciency. A process for dyeing acrylic fibers wherein a low molecular weight polymer .of furfuryl alcohol is added in addition to a naphthol compound constitutes a part of the subject matter of copending application Serial Number 385,682 filed concurrently.

The dye bath is prepared by dissolving or dispersing the various ingredients in a predetermined quantity of water in a conventional manner. While the materials can be added in any order, it is usually advantageous to first dissolve or disperse all other ingredients before adding the naphthol compound. This is because live steam is usually employed in dissolving these ingredients, and if the naphthol is present during this operation, some will be lost by steam distillation.

The dyeing operation is preferably conducted at the boil or at least above a temperature of about 200 F., and, of course, the dye bath should be maintained on the acid side as is customary in dyeing with acid dyes. Any pH of a numerical value less than about 4 is satisfactory with the preferred range being from about pI-I2 to pI-I3. pH adjustments are preferably made with the acid appropriate to the copper salt used, i. e., acetic acid with copper acetate, sulphonic acid with copper sulphate. The dyeing operation should be continued until the desired degree of exhaustion and penetration is obtained. In large scale dyeing this will generally be from about 1 to 4 hours; although in small scale dyeings employing an excess of dyestuff, satisfactory results can often be obtained in from 5 to 30 minutes. As previously mentioned, no close control of the dyeing operation is necessary.

The invention will now be more particularly illustrated by the following examples in which all parts are by weight unless otherwise indicated:

Example I Example II A dye bath was prepared as in Example I, except that 'gm. of Anthraquinone Blue SWF (Prototype 12) was substituted for the du Pont Orange R0. The dyeing was conducted on a 3 gm. sample of material woven from Orlon #81 acrylic filament as before for 20 minutes at the boil. The sample was dyed a dark blue.

Example III A dye bath was prepared by the addition to 300 ml. of water of gm. of Pontacyl Fast Red AS (C. I. 176), 25 ml. of copper sulphate solution containing gms. of copper sulphate per liter, and 1 gm. of beta-naphthol. Dyeing was conducted on a 3 gm. sample of material woven from Orlon #81 acrylic filament for 20 minutes at the boil. At the end of this time the sample was found to have been dyed a dark red.

Example IV A dye bath was prepared as in Example III except that A; gm. of Quinoline Yellow PN (C. I. 802) was substituted for the dye employed in Example III. Dyeing was conducted for 20 minutes at the boil on a 3 gm. sample of material woven from Orlon #81 acrylic filament as before. The sample was dyed a dark yellow.

Example V A dye bath was prepared by the addition to 300 ml. of water of 75 ml. of an aqueous solution of Roracyl Violet 2R containing 1 gm. of dye per liter, 25 cc. of copper sulphate solution containing 120 gms. of copper sulphate per liter, and 1 gm. of alpha-naphthol. Dyeing was conducted for 20 minutes at the boil on a 3 gm. sample of Orlon material. The material was dyed a good violet and the penetration appeared to be excellent.

Example VI Example VII Example VI was repeated except that no copper sulphate was added to the dye bath. At the end of 20 minutes the sample of Orlon material was substantially white. This shows that the cupric salt is necessary for the successful operation of the process of this invention.

Example VIII Example VI was repeated except that a 1.5 gm. sample of a mixed wool-Orlon fabric containing 55% Orlon #41 and 45% wool was substituted for the Orlon sample of Example VI. The sample was dyed a navy blue but on close examination it was found that the wool fibers in the material had absorbed more of the dye than the acrylic fibers.

Example IX A black dye mix was prepared by mixing together 25 liters of an aqueous solution containing 30 gms. of Roracyl Dark Green B per liter, 12.5 liters of an aqueous solution containing 15 gms. of Anthraquinone Blue SWF Conc. 150% per liter, and 12.5 liters of an aqueous solution containing 3.25 gms. of du Pont Orange R0 per liter to give a total of 50 liters.

A dye bath was prepared by mixing together 50 cc. of the above dye mix, 25 cc. of a copper sulphate solution containing 120 gms. of copper sulphate per liter, 300 ml. of water, and 1 gm. of beta-naphthol. To the resulting dye bath there was added a 3 gm. sample of a mixed fabric woven from 55% Orlon #41 and 45% wool. Dyeing was conducted at the boil for 15 minutes. On careful examination it was found that the acrylic fibers and the wool fibers were both dyed black.

Example X To 400 cc. of water there was added 50 mgs. of Pontacyl Fast Red AS (C. I. 176), 2 cc. of a copper sulphate solution containing 120 gms. of copper sulphate per liter and 1 gm. of beta-naphthol. To this dye bath there was added a 1 gm. sample of Orlon staple filament and dyeing was conducted at the boil for 20 minutes. At the end of this time the Orlon was found to have been dyed an excellent red.

Example XI Example X was repeated except that only 0.1 gm. of beta-naphthol was employed. Again excellent results were obtained showing that the concentration of betanaphthol can be varied widely without appreciably affecting the results. Excellent results were also obtained employing 0.1 gm. beta-naphthol as above but substituting for the Pontacyl Fast Red AS (C. I. 176) an equal weight of Anthraquinone Blue SWF (Prototype 12), an equal weight of Quinoline Yellow PN (C. I. 802), an equal Weight of du Pont Orange RO (C. I. 161) and a mixture of 25 mgs. of Quinoline Yellow PN and mgs. of Anthraquinone Blue SWF.

Example XII To 800 ml. of water there was added 1.25 gms. of Pontacyl Fast Red AS, 50 cc. of a copper sulphate solution containing 120 gms. of copper sulphate per liter, and 0.1 gm. of beta-naphthol. To this dye bath there was then added gms. of staple Orlon #41 and dyeing was conducted for 1 hour at the boil. At this time the dye bath and sample were divided equally to give two 400 ml. dye baths. To the first there was added 6 drops of sulphuric acid and to the second there was added 0.1 gms. of beta-naphthol. Dyeing in both was conducted for 1 more hour. While the Orlon samples from both tests were dyed a satisfactory color, it was noted that the addition of beta-naphthol to the second dye bath resulted in a better color of the Orlon sample and'better exhaustion of the dye bath.

Example XIII 500 gms. of Orlon #42 staple filament were loaded into a raw stock dyeing machine and dyed for 3 hours at the boil at atmospheric pressure. The dye bath initially contained 2.5 gms. of the dye Pontacyl Fast Red AS, 5 gms. of copper sulphate, and 5 gms. of betanaphthol in approximately one gallon of water. As the dyeing progressed, additional 5 gm. quantities of betanaphthol were added at intervals until a total of 25 gms. had been employed. The resulting cake was evenly dyed a good red and the exhaustion of the dye bath was excellent.

We claim:

1. A method for dyeing textile materials containing synthetic acrylic fibers which method comprises immersing said material in an aqueous dye bath containing a water-soluble cupric salt capable of furnishing cupric ions, a naphthol compound and an acid dyestuff, said dye bath being at a temperature above about 200 F. and at a pH of a numerical value not more than about four.

2. The method of claim 1 wherein the textile material is a Woven fabric.

3. The method of claim 1 wherein the textile ma-v terial is a mat of acrylic fibers.

4. The method of claim 1 wherein the naphthol compound is beta-naphthol.

5. The method of claim 4 wherein the water-soluble cupric salt is copper sulphate.

6. The method of claim 5 wherein the dyeing is conducted at the boil.

7. The method of claim 1 wherein the naphthol compound is alpha-naphthol.

8. The method of claim 7 wherein the water-soluble cupric salt is copper sulphate and the dyeing is conducted at the boil.

9. A method for dyeing textile material containing synthetic acrylic fibers which method comprises immersing said material in an aqueous dye bath containing from about 1% to 10%, based on the weight of material to be dyed, of an acid dyestufi, from about 50% to 200%, based on the weight of dyestuff, of a water-soluble, inorganic cupric salt which ionizes to give cupric ions in aqueous solution, and from about 2% to 10%, based on the weight of material to be dyed, of a member selected from the group consisting of alpha-naphthol and beta-naphthol, said dyeing being conducted at the boil and at a pH of from about pH 2 to pH 3.

10. A dye bath suitable for dyeing textile materials containing synthetic acrylic fibers said dye bath comprising an aqueous mixture of an acid dye, a naphthol compound and a soluble cupric salt which ionizes to give cupric ions in aqueous solution.

11. Adye bath as in claim 10 wherein the naphthol compound is beta-naphthol.

12. A dye bath as in claim 11 wherein the watersoluble cupric salt is copper sulphate.

13. A dye bath as in claim 10 wherein the naphthol compound is alpha-naphthol.

14. A dye bath as in claim 13 wherein the Watersoluble cupric salt is copper sulphate.

15. A dye bath suitable for dyeing textile materials containing synthetic acrylic fibers said dye bath com- 7 :prgisinglan aqueous mixture containing from about 1% References Cited in the file of this patent to. 10% based on the weight ofmaterial to he dyed, of :an acid dyestufif, from about 50% to 200%, boasedron the Amer. Dyestufi Reporter for November 12, 1951, page weight of dyestufi, of a water soluble, inorganic eupric 750.

salt which'ionizes in aqueous solution :-to give eupric ions, .5 Amer. Dyestuif Reporter for January 22, 1951, pages and from about 2% to 10%, based on the weight of PSI-P54.

material 1Q be dyed, of :a member selected from the Technical Bulletin by du Pont Wilmington Delaware, group consisting of alpha-naphth01 and heta-naphthol. vol. 7 No. 3 for Sept m r 1951, Pagfis 1'47, '16. Adyerbathasinvclaim15=whereinthe water-soluble Amer. Dyestufi Reporter for August 18, 1952, pages icupric :-s alt isi copper sulphate. 

1. A METHOD FOR DYEING TEXTILE MATERIALS CONTAINING SUNTHETIC ACRYLIC FIBERS WHICH METHOD COMPRIES IMMERSING SAID MATERIAL IN AN AQUEOUS DYE BATH CONTAINING A WATER-SOLUBLE CUPRIC SALT CAPABLE OF FURNISHING CUPRIC IONS, A NAPHTHOL COMPOUND AND AN ACID DYESTUFF, SAID DYE BATH BEING AT A TEMPERATURE ABOVE ABOUT 200* F, AND AT A PH OF A NUMERICAL VALUE NOT MORE THAN ABOUT FOUR. 